1. Field of the Invention
The present invention relates to transporting wind turbine blades. More specifically, the present invention relates to a system and method for transporting pairs of long airfoils via railroad using a dual blade sling stand.
2. Description of the Related Art
Large-scale wind turbines are used to generate electrical power. Wind turbines consist of a tower, a generator nacelle, a rotor hub and two or more wind turbine blades. At the time of this writing, wind turbine blades are manufactured in excess of fifty meters in length. Wind turbine blades are one type of airfoil, and airplane wings are anther type of airfoil, for example. Among other modes of transportation, wind turbine blades are transported by railroad, most commonly on rail flatcars. Since the length of a standard rail flatcar is about twenty-eight meters, coupler to coupler, it's clear that two railcars are required to transport a single blade that has a length of approximately 50 meters. The cost of transporting wind turbine components is considerable, and there is certainly a motivation to keep costs to a minimum. These costs include direct railroad expenses for rail transportation, and also include costs associated with building and handling fixtures as well as the cost of loading and unloading wind turbine blades on railcars.
The inventors of the present disclosure have a number of issued patents that address other aspects of wind turbine blade rail transportation. Among these are U.S. Pat. No. 7,591,621, issued Sep. 22, 2009, for Wind Turbine Blade Transportation System and Method, which teaches the use of two railcars and three mounting fixtures to transport a single wind turbine blade. And, U.S. Pat. No. 7,670,090, issued Mar. 2, 2010, for Wind Turbine Blade Transportation System and Method, which teaches the use of three railcars and four mounting fixtures to transport a pair of wind turbine blades. And, U.S. Pat. No. 8,708,625, issued Apr. 29, 2014, for Wind Turbine Blade Railroad Transportation System and Method, which teaches another technique to use two railcars and three mounting fixtures to transport a single wind turbine blade. The entire disclosures of these three patents are hereby incorporated by reference.
It is common for a large number of wind turbine blades to be shipped on a single train from a manufacturer or an intermodal point of transfer to a location near a wind turbine farm. There are opportunities to manage rail transportation costs for wind turbine blades by limiting the number or railcars needed for transport, using mounting fixture efficiently, and minimizing the amount of labor required to load and unload trains. Thus it can be appreciated that there is a need in the art for a system and method addressing the problems related to transportation of long wind turbine blades and other long airfoils via rail.